Apalutamide Data Show Correlation of PSA and Survival in Prostate Cancer

Neeraj Agarwal, MD, a professor in the Division of Oncology, Department of Medicine, at the University of Utah School of Medicine and senior director for Clinical Research Innovation at Huntsman Cancer Institute, discusses how the prostate-specific antigen (PSA) responses correlate with survival outcomes in 2 phase 3 trials of apalutamide (Erleada) in patients with advanced prostate cancer.

The trials evaluated for these data were the TITAN trial (NCT02489318), which investigated patients with metastatic castration-sensitive prostate cancer, and the SPARTAN trial (NCT01946204), which looked at patients with nonmetastatic castration-resistant prostate cancer (CRPC). Both studies were double blind and placebo controlled.

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0:08 | What we did in this analysis was to look for the degree of PSA responses and correlation of PSA responses with survival outcomes. The PSA decrease of 90%, which is a validated way to assess PSA response, so PSA 90% or undetectable PSA, which is PSA of less than 0.2 ng/mL, were considered standard measures of PSA responses in our study. Patients in both studies, in TITAN and SPARTAN, when they had these PSA responses [of] PSA 90% or PSA of less than 0.2 ng/mL, we correlated these responses with survival outcomes.

1:10 | Let's look at the results. We included 525 patients from the TITAN study who underwent treatment with apalutamide, and we included 806 patients from the SPARTAN study—so all patients in TITAN and all patients in SPARTAN who had treatment with apalutamide. Let's look at the PSA 90% responses first. A majority of patients in the TITAN study, 72% of patients, achieved a PSA 90% response, which is remarkable. Even in the SPARTAN trial, which was a CRPC population, meaning these patients had already had disease progression on androgen deprivation therapy, 62% of patients achieved PSA 90% response. If you look at undetectable PSA rates in the TITAN study, 67% of patients achieved undetectable PSA rates. In the SPARTAN study, again, which is a CRPC population, around 40% of patients—38% patients to be precise—achieved undetectable PSA responses.

2:46 | Let's see how these PSA responses correlated with survival outcomes. So, progression-free survival in the context of TITAN study was a radiographic progression-free survival. In the context of SPARTAN, it was metastasis-free survival, and both are surrogate for overall survival. So in the TITAN study, 90% PSA responses were associated with a 55% reduction in risk of death. In the SPARTAN study, 90% PSA responses were associated with 65% reduction in risk of disease progression.

3:35 | Let's look at the undetectable PSA rates and how these correlated with overall survival outcomes. So, if you look at the TITAN study, 67% of patients achieved undetectable PSA, that is PSA of less than 0.2 ng/mL. In the SPARTAN study, 38% of patients received or achieved undetectable PSA rates. And in both cases, if you achieved undetectable PSA, you had patients who are likely to have or experienced 80% reduction in risk of death.